The present invention relates to new copolymers based on one or more ethylenic monomers and at least one mono-, bis- or trismethylolphenyl allyl ether of the formula I. ##STR2## n being from 1 to 3.
The present invention also relates to a process for the preparation of these copolymers and to their application in the preparation of coatings, particularly in the fields of paints, varnishes, inks and adhesives.
Compound (I) is well known in the field of paints and varnishes. It is employed as a crosslinking additive to resins such as epoxy, phenolic, vinyl, polyester or aminoplastic resins, to which it imparts great hardness. In addition, it improves the adhesion and the flexibility of the coatings made using these resins. See, for example, U.S. Pat. Nos. 4,098,745 and 4,164,587.
However, the use of compound (I) presents many disadvantages.
Thus, the preparation of the coatings in which it is present requires a final stoving operation which must be carried out in the presence of an acidic catalyst such as orthophosphoric acid at temperatures above 165.degree. C.
Use of compound (I) in the electrophoresis bath formulations is also known. In European Pat. No. 82,214, for example, compound (I) is added to an epoxyamine adduct. After neutralization with acetic acid, the mixture thus produced is employed in the preparation of a pigmented electrophoresis bath. A bath of this kind has poor stability. In fact, under the influence of the acid, acetic acid in this case, compound (I) partly condenses with itself, producing a release of formaldehyde. As a result, the adduct behaves like a thermoplastic. Compound (I) cannot therefore be employed in an acidic medium nor, consequently, can it be employed in cataphoresis.
Another deficiency of compound (I) lies in its poor pigment-wetting power when it is employed as an additive mixed into a formulation, for example a paint formulation. As a result, the high homogeneity which is essential if the best gloss, adhesion and chemical resistance properties are to be attained, cannot be obtained in these formulations.